Airships have a long and storied history, even predating that of the airplane. For purposes of this invention, airships are described as any atmospheric vehicles which displace an amount of air at sea level that is greater in mass than a mass of the vehicle, such that lift forces are generated greater than the mass of the vehicle at the surface of the Earth. Furthermore, for purposes of this invention airships are limited to atmospheric vehicles which have at least some degree of steering control such that the vehicle can be navigated through the atmosphere to at least some extent.
Airships have almost exclusively in the past been limited to the lower atmosphere where the higher density of air has allowed such airships to be provided with heavier structures and/or greater payload without excessively large balloons thereon. High altitude balloons are known which travel through the stratosphere and into the mesosphere. However, such balloons at best might have some form of ballast or other altitude control, but without steering control and propulsion for navigation over the surface of the earth, or control merely for station keeping over a single point.
One persistent problem with high altitude balloons is the difficulty in successfully launching them without damaging the large balloons during launch. Even small winds acting upon the large surface area of such balloons, coupled with the relatively lightweight and correspondingly weak structures which can be provided and still maintain high altitude operation are highly susceptible to damage during launch. Not only is the launch phase difficult, but also during ascent various lift and drag forces acting on the balloons can cause the balloons to interact unfavorably with structural portions of the vehicle.
Typically, to solve this problem in the lower atmosphere, balloons or other gas containing envelopes on an airship are contained within an outer envelope. For high altitude performance, the weight associated with such an outer envelope is a luxury that comes with significant weight penalty, thereby making high altitude performance either impossible or the payload provided significantly reduced. Accordingly, a need exists for a high altitude airship which can effectively be launched from the ground, travel safely to high altitude above the stratosphere with a propulsion system able to provide propulsion for steering and navigation of the airship above the stratosphere.
There is a great demand for high altitude airships. They promise to play a critical role in intelligence gathering and telecommunications. This need is exemplified by the Department of Defense of the United States recently turning to the use of free drifting balloons to accomplish goals that could be met by a high altitude airship more effectively, such as gauging wind speeds at various different altitudes for the benefit of operation of remotely piloted drones or other vehicles. The high altitude airship of this invention can provide limited maneuverability, altitude holds, payload infrastructure support and other benefits of the airship while being low cost and easy to deploy and operate.
Prior art attempts at moderately high altitude airships include airships described in U.S. Pat. Nos. 6,609,680 and 6,607,163. Such airships are generally limited to operation in the upper stratosphere, where winds are greater and station keeping less successful. Also, the complexity of such prior art medium high altitude airships have increased their cost and difficulty of launch, leading to less than widespread use.